The present invention pertains to cellular communication systems and more particularly to a method for conserving power and system capacity during peak communication system loading.
In current cellular systems, target Frame Erasure Rate (FER) settings and power control parameters are set statically and are independent of the actual load on the system which is dynamic. The FER measures dropped frames or quality of a link in a communication system.
In a CDMA system, there is a strong relationship between system capacity, RF power, interference, and call quality. As call quality is increased, the power consumed by the system tends to increase. This situation consumes available cell power which is limited, and increases system interference which in turn reduces system capacity from an RF perspective. This is a particularly important aspect of efficient CDMA systems.
Call quality in this context includes voice quality which can be measured by frame erasure rate; mean opinion score (MOS score) which is a measure of voice quality; data throughput for data services; and call reliability which includes call setup success rate and the dropped call rate. This relationship is well know to those skilled in the art. Therefore, there is a fundamental tradeoff between call performance (FER/quality, call reliability, and messaging reliability) and system capacity. As the link performance is increased FER is typically lowered, additional power is consumed, interference is generated, and capacity is reduced.
Cellular systems are therefore often tuned to handle the capacity requirements during the busiest period of the day, sacrificing call quality and reliability for additional peak capacity. A cellular system may be tuned as an aggregate. That is, the same parameters may be used statically over the entire system, even though the loading, call performance, and radio link characteristics may vary significantly over the system.
In addition, the loading characteristics can vary substantially even over short periods of time on a per cell basis. The distribution of load or call traffic over the system is in most cases highly non-uniform both temporally and geographically. This makes it difficult to optimize the tradeoffs between system capacity and call performance using static parameters relating to system capacity, power control, FER, and call quality. The current approaches are based only on achieving a given target FER. Such approaches are not based on available or utilized system capacity.
Therefore it would be highly advantageous to have a method for adaptively varying power control related parameters as a function of system load.